This invention relates generally to turbine casing construction and, more particularly, to a flow sleeve mounted on the inner surface of an outer turbine shell in a double-shell turbine engine design.
In order to maximize efficiency and performance in a gas turbine engine, clearances between rotating (e.g., rotor) and stationary (e.g., stator) components should be kept to a minimum. Such clearances, however, should also accommodate expansion and contraction of the rotor and stator due to changing temperatures of the components and the changing speeds of the rotating components during the various operating conditions of the engine. For example, the rotor and stator components will radially expand as temperature increases, while the rotor components will also expand or contract with speed changes.
A variety of systems have been utilized to adjust and maintain radial and axial clearances during all conditions of turbine operation, including air distribution systems that feed cooling and heating air onto the rotor and/or stator elements. Generally, the air is taken from the air compressor of the gas turbine engine and may be distributed onto turbine blades, turbine wheels, casings, or turbine stator carrier rings. Depending upon the particular objective, air may be tapped from various stages of the compressor, or may be taken from the combustion chamber enclosure to supply the necessary heating air. The air supply systems may be provided with regulating valves so as to modulate the air flow and the temperatures by mixing air from the different sources.
Such systems have not been satisfactory in all respects, however, especially with respect to the inside surface of the outer shell or casing in a double-shell gas turbine configuration.